Unfortunately there isnt' a local hardware store (I am fairly rural), and the electronics shop in the nearest city shut down a few years ago. Will take a look at mcmaster.com, or take a stab on some amazon cog sets :)

I want to attach this to a cog/something to turn it into a pulley (see my other post from months ago about a chicken door). Thing is there's loads of cheap cog kits on amazon, but they are all for circular shafts, not a flat ended one like this.

Is there an online shop where I can get bits for the physical attachment of things like this?

So will give that a go on Friday. The next step is to get some sort of small solar panel and charge unit, seem them for around £6 (I may need to bug you again Gordon!). Just to keep things topped up.

Short term I think it'll just be an LDR and sitting outside with my laptop takin g measurements for door opening Vs closing times. Eventually I'd like to link to WiFi, have a minimum opening time of 7am, and then something ~45 minutes after sunset. LDR is cheaper and doesn't involve me doing the WiFi/cat5 to our garden (longer term plan regardless). Oh and to report that the door is open and closed (WiFi could also periodically sync the time).

Once the motor is working on the door it'll just be two reed switches to ensure door opens and closes at the right point rather than relying on timing which could go wrong, or something could slip (I think commercial systems just rely on time and calibration - maybe good enough, bit reed switches aren't expensive!).

I'll write up the chicken door at some point. Theres a couple of Arduino examples. But it would be good to get an espruino example shared because it's such a great project and I've done it with very little experience and knowledge (except my JS).